Protractor.



P. OLMSTED.

PROTRACTOR APPLICATION FILED AUG-2.1916.

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PERRY OLMSTED, OF LOS ANGELES, CALIFORNIA.

PRGTRACTOR.

Application :tiled August 2, 1916.

To all whom t may concern Be it known that I, PERRY OLMs'rnD, a citizenof the United States, residing at Los Angeles, in the County of LosAngeles and State of California, have invented a new and usefulProtractor, of which the following is a specication.

The principal objects of this invention are to provide a protractor ofexceedingly simple and convenient construction constituting' not only aprotractor, but also a trisquare, bevel square, center square, anglefinder, and also a simple means whereby without the use of mathematicsof any kind, or even tables, the length of the side of any regularpolygon to be inscribed in a circle can be determined; to provide aconstruction by which an angle of any size can be bisected in a verysimple manner; in which the angle between the movable straight edge andthe stationary straight edge of the protractor can be brought to a sharppoint at all small angles; in which a micrometer arrangement is providedwhereby settings down to degrees and less, if desired, can be madewithout the necessity of division lines so close together as to requirethe use of a glass; in which means can be provided whereby the movablestraight edge can be set conveniently to certain specified angles, asfor example, ninety and forty-five degrees without the necessity ofobserving the scales sothat this can be done where the light isinsufhcient and yet provide a device which can be folded up into a smallcompass. The invention also involves other features including theprovision of a scale in combination with the usual degree scale lwhichwill show the number of inches rise per foot at any desired angle, andwhich can be made to show the various angles necessary in buildingconstructions, as for example, theheel out, plumb cut, and side cut ofrafters for a hip roof at various angles.

Reference is to be had to the accompanying drawings in which- Figure lis a front elevation of a preferred embodiment of the invention showinghow an angle is bisected by it;

Fig. 2 is an end view showing certain details;

Fig. 3 is a view of the rear side of the protractor showing how it isused for finding various angles necessary in constructing roofs and thelike;

Fig. t is a front view showing the use of Specification of LettersPatent.

Patented Nov.l 2*?, limit.

serial no. 112,688.

the device in finding a rise in inches per foot;

F ig. 5 is a similar view showing the setting of the two movablestraight edges at ninety and fortylive degrees respectively, and showingsome modifications.

Fig. G is a view similar to Fig. 1, showing a modified form, and showingthe application of the instrument to the problem of inscribing a polygonin a circle, and

Fio'. 7 is a similar view showing another modification.

Referring lirst to the lirst sheet of draw ings, it will be seen thatthe invention is shown in a form in which the instrument comprises aplate or beam a having a pivot and provided with a straight edge cextending from said pivot in one direction. This beam is also providedwith a parallel straight edge CZ offset from the straight edge c andextending a-s far as the pivot from the opposite end of the plate. Itwill be seen that on this beam is a protractor comprising asemi-circular angle scale e and in the form shown on this sheet thisscale is divided up into divisions of ten degrees each. Also inside thisouter scale e is a semi-circular scale 7, the degrees on which are notnumbered, but which is divided in a similar manner except that thepoints of division are halfway between the points of divison on theouter semi-circular scale, and from each one of them two lines g aredrawn one to each of the two adjacent points marked on the scale c.These lines g are of importance as will appear. The protractor is shownas having its diameter laid olf on a straight line of which the straightedge c is a part.

Furthermore this side of the device is shown as provided with anotherscale which, in the form shown, Consists of three parts, one 7i parallelwith the straight edge o, and the other two perpendicular to it. Thesescales are divided up into equal divisions and the three scales takentogether extend entirely around the semi-circle. The purpose of thiswill be described hereinafter.

Frictionally pivoted atl the central point o are two arms 1 and Z. Oneis shown as on the back and the other on the front. They are providedwith semi-circular offset portions covered by the fastening nut andwasher m, but their inner straight edges are exactly in alinement withtbe center of this pivot on which they are adapt-ed to swing. It will benoticed that the two straight edges c and Z are at a distance apartequal to the width of these two arms if; and Z so that when they arefolded together and brought into contact with the edge c the wholeinstrument is of rectangular form7 and .all the parts come within therectangle.

Referring now to the pivoted arm which is on the front, it will be seenthat its inner straight edge is scaled in inches and twelfths and thatit extends beyond its pivotal point and is provided with four divisionmarks a at equal distances apart. These divide up the space between thetwo graduated circles c and j into live equal divisions. In this formthe line along which these marks are located is radial, that is in exactaline-ment with the center Z). The object is to provide a micrometerarrangement whereby the protractor can be divided into a liner degree ofdivision than that indicated by the division points thereon. This willexplain why the lines g are not radial, but have a certain slant. Y

In the use of the instrument for this purpose the pivoted arm L can bebrought for example tothe point indicating` seventy degrees with itsstraight edge on that division of the outer circle, and then its anglewith the straight edge 0 will be just seventy degrees, but if it isdesired to mark off seventj two degrees it is moved over further untilthe second of the division marks n, on its .shortarnn registers with theline g extending fromthe seventy degree point of the outer circle to thenext point on the inner circle. In this way aline division can b esecured without necessitating the use of iner graduated marks on theouter circle. These divisions on the short arm ot the member /c are muchfarther apart than the corresponding divisions would have lto be on thecircle e. In the size shown, angles involving` divisions under thirtyminutes can be readily estimated, and this is liner than is usuallynecessary in carpenter work. To facilitate the use of this part of thedevice the space between the circles c and 7" is divided by iveconcentric circleslspaced equally.

rl`he use of the scales 7L is also very practical for they are dividedup into equal divisions to indicate rises in inches per toot. The firstdivision on the right indicates that if the straight edge 7a is set tocorrespond with that division it gives a rise of one inch `per foot, andso on throughout the scale.

The divisions on the two vertical scales are exactly equal to eachother. The divisions on the scale j shown in these igures constitute acontinuation of the two scales 71..

In the use of this device for bisecting angles, the two arms Z2 and Zhave to be employed and for the purpose of using` them .withoutreference to the back not' the instrument one'o'f them, as for exampleZr, can be set to the vangle desired, as for example thirty degrees, andthen the rear one Z brought into register with it, then the front one 7ccan 4be moved to the fifteen degree angle which will bisect the angleformed by the arm Z, the short arm of the member Za being used formeasuring the angles in both cases.

Where it is desired to find the facts about a polygon to be inscibed ina circle, the instrument is used as shown in Fig. 6. First, .the centralangle subtended by one side of the polygon is obtained. For example, ifit is an Octagon, this angle is forty-Jive degrees. The arm 7a is set atan angle of forty-live degrees from the straight edge c. N ow the lengthof the radius of the circle in which it is to be inscribedis laid ott onthe straightfcdge c, measuring from the center Z), and also on theadjacentstraight edge of the member r from the same point. Theinstrument is so placed, as indicated in Fig. 5, that these two pointson the straight edges c and will be located on the surface of thecircle, and then these points marked in any desired way. This gives theends of one side of the polygon and the remainder of the figure can belound in any desired way. rllhe geometrical figure appearing on Fig.proves without any mathematical ldemonstration that this process iscorrect.

Another feature ot the instrument shownin Figs. l and 2 is a bar oadapted to t either on the straight edge c Vor on one of the arms u-orZ. It has a groove o adapting it to lit rictionally. Its use is topermit the completion of a' sharp angle, as indicated in Fig. 1.TWithout it the apex of the angle would be lilled by the washer. j

@n the rear of the beam are placed scales formed to provide for showingvarious angles, as may be desired. For example, on the irst scale p atthe top are ltwo sets of lines indicating the plumb cut and `end cutrespectively of the rafters ot a hip roof. For example, if the hip roofhas a pitch of seventeen inches to the foot the angles at which theplumb cut Vand end cutare to be made are indicated by the lines marked17 on this scale. Various other things can be shown at this place, asfor example, the

butt cut and miter cut of chords used in constructing polygons orportions of 1polygons, as for example, in the making of a bay-window. Inthis case the second scale g is shown as marked in this way. The iningvemployed to assist the operator in fget- Corresponding cuts for otherlll@ pas

Leanser) en ting the proper angles to mark off on his work.

Another way in which the instrument can be used is in sighting along thestraight edge of a pivoted arm if: or Z to get an angle, especially anangle of elevation. For this purpose the beam is placed in horizontalposition, a level being used, and the arm to be sighted along is tippedto the proper angle and the sight taken along it to the point indicated,as for example, the top of a building` or the like. Then the angleindicated without change in the position of any of the parts is readdirectly on the protractor.

The instrument can be used in other ways for various measuring purposes.

For the purpose of setting the arms at the most common angles, as forexample, ninety and forty-five degrees, each one is provided with aprojection having a straight edge, as for example, le and Z at ninetydegree and forty-five degrees respectively t0 the straight edge. Then asshown in Fig. 5, the operator can readily bring this edge intoregistration with the straight edge c by his lingers without looking atthem. Therefore the arms can be set in the dark if desired. This ligurealso shows some modifications in markings. VThe lines g are replaced bylines g all slantin g in the same way instead of alternating. The scale71. in this case is provided with divisions equal to the divisions onthe scales As half of it is just equal in length to a scale y',complementary angles can be found by placing one arm to read on onescale and the other at the correspondingly numbered division on theother` This brings them just ninety degrees apart. The scales y' shownin Figs. 1 and 5 can of course be put on the same beam.

Fig. 6 has been referred to for the purpose of showing one use of theinstrument, but this figure shows a modification in that the arm h',instead of being provided with a straight edge on its short arm inalinement with the pivot, is provided with an edge h2 at an anglethereto and in this case the lines g2 which correspond with the lines gof the first ligure are radial. In this case the reading of the angle isdone in the same way as before and the result is equivalent. Tn thisform the four semi-circles between the circles e and f are omitted asthey can be if desired in any of the forms.

Fig. 7 shows another modication in which the straight edge is located inan angular position in a di'erent way, but also equivalent to the otherforms.

lt will be seen that all these features of utility are secured by aninstrument which has only three or four elements and which ispractically as simple as any form of trisquare or protractor that hasany moving parts at all. This is an important advantage of the devicebecause when not in use it can be folded up into avery compact form,both arms 7c and Z registering with each other and occupying the space just beyond the straight edge c. 1n this way it can be carried around inthe poclreV as it has no projecting parts. lt is no more trouble than anordinary two-foot rule.

Although T have illustrated and described only a few forms of theinvention T am aware of the fact that other modifications can be madetherein by any person skilled in the art without departing from thescope of the invention as expressed in the claims. Therefore l do notwish to be limited to any of the forms shown, but what l do claim is- 1.As an article of manufacture, a measuring device comprising a beamhaving an angle scale thereon, and an arm having a straight edge pivotedat the center of said scale, the beam having a straight edge and aplurality of scales thereon having identically marked divisionsindicating the pitches of hip roofs, and showing the positions at whichthe arm should be set to give, between it and said straight edge on thebeam, the angles of the several cuts for the rafters of the hip roof.

2. As an article of manufacture, a plate having a semi-circularpretractor scale, an arm pivoted at the center of said scale and havingat each end a scale perpendicular to a diameter of the protractor scaleand divided into equal divisions each indicating a rise of an inch perfoot, and a third scale connecting the other two and so located that thethree inclose the protractor scale, and also indicating rises in inchesper foot, said third scale constituting a continuation of the endsca-les.

3. An article of the class described, having a circular angle scalethereon and a straight edge in alinement with its center provided with ascale extending from said center, and an arm having a straight edgepivoted so that the latter straight edge is in alinement with saidcenter, said arm having a projection beyond the center also providedwith an edge in alinement with the straight edge of the arm, said anglescale being provided with an inner circle divided up into divisionsequal in angular length to the divisions on the outer circle andconnected with them by lines, the projection from said arm having anedge thereon equal to the distance between said circles radially andhaving equal divisions thereon, the last named edge and the linesbetween said circles being located at an angle to each other in allpositions of the arm, whereby said arm always intersects one or more ofsaid lines, and whereby the point of intersection indicates the fractionof the angular distance of the arm from the adjacent division on theouter circle.

4. An article of the class described provided with a pivot, a scalearranged about said pivot as a center and having an outer curve and aninner curve, the outer curve being divided into equal divisionsrepresenting multiples of one degree, and the inner curve being dividedinto divisions each representing the same number of degrees as the oneson the outer curve, straight radial lines connecting the divisions onthe inner curve with the adjacent divisions on the outer curve, and anarm pivoted to the main member at said center and having a non-radialedge provided with a scale thereon equal to the distance between saidtwo curves and divided into a number of equal divisions whereby it canbe read on said connecting lines to indicate jactions of the divisionson the outer curve. 4

5. An article of the class described, comprising a main member or beamand two arms pivoted thereto on the same axis, said member having aprotractor on one side, and one of said arms having anextension beyondthe pivot adapted to pass over said lprotractor as the arm swings toindicate the angle that arm makes with respect to the base of theprotractor, said beam having a straight edge in line withsaid base, theother arm also being set by bringing it into registration with the armhaving the extension.

6. Anarticle of the class described, comprising a main member or beamand two arms pivoted thereto on the same axis but on opposite sides,said member having a protractor on one side, and the arm on that sidehaving an `extension beyond the pivot adapted to pass over saidprotractor as the arm swings, whereby an angle can be bisectedconveniently by setting the front arm twice, iirst to the angle itself,and second to half the angle and at `the time of the irst settingbringing the rear arm into registration with it and keeping it there.

7. An article of the class described, hav ing a main member and an armpivoted thereto,.each having a straight edge, anda member having agroove in one edge adapted to -iit on one straight edge, ;the oppositeedge of said member being parallel with the groove, whereby said `memberis adapted to make a complete sharp angle with'the other straight edge.a

In testimony whereof I have lhereunto affixed my signature. Y

PERRY .OLMSTED Copies of this patent may be obtained for five centseach, by addressing thevommissoner Vof Patents.

Washington, D. C.

